Apparatus for butt welding thermoplastics sheets and films

ABSTRACT

Improvements in the process and apparatus of application Ser. No. 236,766 Mar. 21, 1972. There is described a technique for butt welding a trailing end of one roll of thermoplastic film or sheet material to the leading edge of another roll of such material by vertically superimposing the trailing and leading portions of the two rolls, aligning the lateral edges of such portions over a significant distance sufficient to insure angular alignment of the two rolls at the butt weld. Severing the two portions along a coincident transverse line, heating the severed portions to an extent sufficient to weld such together, and bringing the heated transverse edges of the two portions together while maintaining lateral edge alignment of said portions, whereby butt welding such into a continuous sheet.

p 1974 D. E. JOHNSON 3,834,971

APPARATUS FOR BUTT WELDING THERHOPLASTICS SHEETS AND FILMS Filed Sept.21, 1972 United States Patent Oifice 3,834,971 APPARATUS FOR BUTTWELDING THERMO- PLASTICS SHEETS AND FILMS David Emil Johnson, Macedon,N.Y., assignor to Mobil Oil Corporation Filed Sept. 21, 1972, Ser. No.291,133 Int. Cl. G03d 15/04 US. Cl. 156-507 5 Claims ABSTRACT OF THEDISCLOSURE Improvements in the process and apparatus of application Ser.No. 236,766 filed Mar. 21, 1972. There is described a technique for buttwelding a trailing end of one roll of thermoplastic film or sheetmaterial to the leading edge of another roll of such material byvertically superimposing the trailing and leading portions of the tworolls, aligning the lateral edges of such portions over a significantdistance sufiicient to insure angular alignment of the two rolls at thebutt weld. Severing the two portions along a coincident transverse line,heating the severed portions to an extent sufficient to weld suchtogether, and bringing the heated transverse edges of the two portionstogether while maintaining lateral edge alignment of said portions,whereby butt welding such into a continuous sheet.

This invention relates to butt welding films or sheets of thermoplasticmaterial It more particularly refers to a process and apparatus forcarrying this out in an improved manner.

Application Ser. No. 236,766 filed Mar. 21, 1972, now US. Pat. No.3,769,124 described a technique for butt welding a leading edge of oneroll of foam polystyrene sheet material to a trailing edge of anotherroll of similar foam polystyrene sheet material. According to this priorapplication, the contents of which are incorporated by reference; aportion of the leading edge of a first foam sheet is transverselysevered by contacting such with a moving hot element; a portion of thetrailing edge of a second foam sheet is transversely severed bycontacting such with further movement of the same hot element; the twotransverse heated severed edges are then butted and welded together.

While this process, and the apparatus which is used to carry it out,performs its intended function very well, it has been found in practicethat there sometimes occurs a canting of one sheet with respect to theother. Since the thermoplastic sheet material in question here isusually wound on rolls in a less than absolutely laterally alignedfashion, the end of one roll may be laterally displaced with respect tothe beginning of the next roll. In the process and apparatus of theabove referred to prior application, the two sheets to be butt weldedare aligned along the line where the transverse severing will beaccomplished and are vertically spaced apart, the hot wire severingmeans passes vertically through both sheets sequentially and the sheetsare brought together while the severed transverse edges are hot enoughto weld on contact. Where there is lateral displacement of the rolls,the welded edges are canted, or angularly displaced, with respect toeach other. FIG. 1 of the accompanying drawing shows this condition in amuch exaggerated form.

It is therefore an important object of this invention to provide a novelprocess of butt welding two sheets of thermoplastic material.

It is another object of this invention to provide a novel apparatus forcarrying out this novel process.

It is a further object of this invention to provide a novel techniquefor angularly aligning two sheets of thermoplastic material.

Other and additional objects of this invention will be- 3,834,971Patented Sept. 10, 1974 come apparent from a consideration of thisentire specification including the claims and the drawing hereof.

Understanding of this invention will be facilitated by reference to theaccompanying drawing in which:

FIG. 1 is a perspective diagrammatic representation of the problemencountered by the piror art;

FIG. 2 is a vertical schematic view of the process and apparatus of thisinvention;

FIG. 3 is a plan schematic view, with appropriate parts broken away, ofthe process and apparatus of this invention; and

FIG. 4 is similar to FIG. 2 showing the process at the point of buttwelding.

In accord with and fulfilling these objects, one aspect of thisinvention resides in a process comprising: providing a trailing portionof a first length of thermoplastic film or sheet, of substantially thesame width as said first sheet, vertically displaced from said firstsheet; overlapping a significant length of said two sheets; verticallyaligning the respective lateral edges of said two sheets over saidsignificant length; sequentially severing said two sheets alongsubstantially identical transverse lines within said significant length;discarding the forward severed portion of one of said sheets and therearward severed portion of the other of said sheets; heating theremaining severed transverse edges; and bringing such heated transverseedges into abutting relationship, whereby butt Welding said sheetstogether in substantial lateral axial and vertical alignment.

As noted in the proir referred to patent application, the preferred formof film or sheet for use in this invention is foam form and thepreferred thermoplastic material is polystyrene. The preferred severingtechnique is by means of a hot wire which passes downwardly through thetwo sheets sequentially to sever the forward and rearward portionsreferred to above. After discarding these severed portions, the hot wirepasses upwardly again heating the transverse severed ends sufiicient topermit them to butt Weld together.

In order to laterally align the superimposed portions of the two sheets,upstream and downstream vertical guides are provided extending more thanthe vertical distance between the two sheets. The guides are on at leastone lateral side of both sheets and means are provided to bear bothsheets against the guides. The guides are streamwise spaced apart asignificant distance as aforesaid. In a preferred embodiment of thisinvention two pairs of vertical guides are provided. One pair isupstream, disposed on each lateral side of both sheets, while the otherpair is downstream, disposed on each lateral side of both sheets.

In a preferred embodiment of this invention, the downstream vetricalguide means is pivotally joined to a wheel means operatively associatedwith one of the sheets, preferably the trailing portion of the firstlength of sheet. As the sheet Moves laterally, it tends to force thedownstream vertical guide to move in the same lateral direction. Thismotion is translated through a series of lever means to the wheel means.Where there is no lateral displacement of the downstream vertical guidemeans, the wheel means axis is substantially transverse to the sheetaxis. As the downstream vertical guide means is moved laterally, theaxis of the wheel means is proportionally canted in the oppositedirection whereby tending to drive the sheet back toward a morecentrally disposed lateral alignment. This guide and compensating meanseases the burden of laterally aligning the two sheets being butt weldedby minimizing the lateral off-set of one with respect to the other. Itis preferred that the upstream vertical guide means is disposed upstreamof the wheel means referred to above and that there be no controllinkages between this upstream vertical guide means and either thedownstream vertical guide means or wheel means. If desired, however,

control linkages can be provided between these various means.

It is considered to be the principal purpose of this process andapparatus to butt splice two sheets of thermoplastic material withoutinterrupting the flow of the process in which the sheets are being used.For example, the first sheet referred to above is preferably the end ofa. roll of such sheet material which is being fed into further processinThe butt welding of these two sheets referred to above is preferably thestart of a second roll of such sheet material which will be fed into thesame further procesing. The butt welding of these two sheets together isfor the purpose of carrying out the referred to further processingwithout roll change interruption. In order to accomplish this, thefeeding of the sheet off the roll into the further processing must be insuch manner as to provide sufficient time to make the butt splicereferred to herein. This can be accomplished through the use ofintermittent feed, with sufficient time lapse between feeds to make thesplice. Intermittent feed can be accomplished in a conventional mannervia engaging/ disengaging roll pair means with either the driven or theidler roller moving into and out of contact with the sheet being fed.Alternatively, intermittent feed can be conventional means of the pulltype, where a length of sheet is pulled from the roll, the pulling isstopped until the pulled length is used up in further processing andthen additional length of sheet is pulled from the roll. Otherconventional intermittent feed means are available and will suggestthemselves to those skilled in the art.

'In any case, and regardless of what intermittent feed means is used,the drive for this feed means is preferably between the butt weldingmeans of this invention and the further processing means being fed. Thebutt weld referred to herein must be made during the short time intervalwhen no sheet is being fed to the further processing.

The splicing, or butt welding referred to herein can be initiated andcontrolled manually or automatically depending upon the particularpreference of the user. Sensing means can be provided associated withthe first sheet to sense that the end of the sheet is approaching and toactivate the splicing technique referred to herein. This sensing can bemechanical, as by means of a mechanical feeler on the roll of firstsheet set to judge the ending of the roll, or an electric eye set toaccomplish the same purpose, or a length counter to determine how muchof a standard length roll has been used up.

The second sheet roll is suitably positioned so that the startingedge-of this sheet is above the trailing end of the first sheet, butthis need not be so. If for some reason it is desired, the verticalpositions of the two sheets can be reversed.

It is within the scope of this invention to provide means for removingthe severed front and rear ends of the two sheets. This can beaccomplished by tension activated reverse spinning rolls operativelyconnected to the scrap front and/or rear pieces of sheet respectively.Alternatively scrap can be pulled out of the apparatus by hand.

Referring now to the drawing, and particularly to FIG. 1 thereof, theprior art problem is shown exaggerated in which a first sheet is buttwelded 12 to a second sheet 14. It should be noted that while thelateral edges 16 and 18 respectively, of the two sheets align at thepoint of the butt weld 12 the axes 20 and 22 respectively of the twosheets are not coincident whereby causing the sheets to be canted withrespect to each other.

FIGS. 2, 3, and 4 show the butt splicing process and apparatus of thisinvention. A first sheet 10 passes through the nip of a pair of rollers24 and 26 which form an intermittent drive means. A second sheet 14 ifed into the butt splicing means from a new roll 38 thereof. Two pairsof vertical edge guides 30, 32, 34 and 36 are provided with a pair ofeach, 30 and 34, and 32 and 36 respectively, spaced upstream anddownstream a finite,

reasonabledistance apart and defining the lateral extent of the sheets10 and 14 between guide pairs 30 and 36 and 32 and 34 respectively. Itshould be noted that the downstream pair of vertical guides 32 and 34are laterally floating. This pair of guides is pivotally 38 connectedthrough a linkage 4.0 to a guide wheel 42 which is itself pivotallymounted 41 so as to point its direction of rotation proportionallyopposite to the lateral float direction of the downstream vertical guidepair.

The first sheet 10 passes over a lower clamp means 48 and 5t}, and belowa frame 52. The second sheet 14 passes over the frame 52 and below aclamp 54 and a vacuum means 56. For temporarily holding the second sheet14 in streamwise position without preventing its lateral alignmentmotion consistent with the position of the vertical guides, a spike 58is provided to penetrate the second sheet 14. Other temporary holdingmeans can be used to replace this spike.

A resistance wire 60 is provided initially disposed above the secondsheet 14 but adapted to pass downwardly through both the second and thefirst sheets respectively to sever each in substantially identicaltransverse alignment, and then to pass upwardly past the severed ends.The wire 60 is heated by resistance heating via current input (notshown) sufficient to melt cut the sheets and heat the cut edges enoughto permit butt welding thereof.

In the operation of the depicted device, the vertical guides 30, 32, 34and 36 laterally align the first and second sheet. The hot wire passesdown through the two sheets transversely cutting them while the lower orfirst sheet is held between the frame 52 and the downstream lower clamp48 and the upper or second sheet is held by the vacuum means 56. Thetrailing, severed end of 62 of the lower or first sheet is ejected whilethe severed transverse edge of the second sheet is brought down intoproximity to the severed end of the first sheet. The hot wire passesupwardly past the two severed ends, heating such to thermoformingtemperatures and the two heated ends are butted by the vacuum meansbringing the second sheet against the upstream most lower clamp 50 asshown in FIG. 4.

What is claimed is:

1. Apparatus comprising means for feeding a first, lower sheet into thenip of a pair of rolls; intermittent drive means operating said rollsdrawing said first sheet therethrough; means for feeding a second, uppersheet into proximity to said lower sheet and said pair of rolls; upperclamp means associates with said second sheet; lower clamp meansassociated with said first sheet substantially vertically aligned witheach other; heating and cutting means proximate to said clamp meansmovably positioned to pass through both said first and said secondsheets; means to move said clamp means toward each other and thereby tobutt said sheets in end to end relationship; and upstream and downstreamspaced vertical guide means disposed adjacent at least one lateral edgeof both of said sheets, one of said guide means being transverselymovable with respect to said sheet, said guide means being adapted tolaterally and axially align said sheets.

2. Apparatus as claimed in claim 1 wherein said vertical guide meanseach comprise member adjacent both lateral edges of both sheets.

3. Apparatus claimed in claim 1 including an upstream pair of verticalguides, one on each side of said sheets, and a downstream pair ofvertical guides, one on each side of said sheets.

4. Apparatus as claimed in claim 3- including pivotally mounted guidewheel means operatively associated with said first sheet and pivotallylinked to said downstream vertical guide pair.

5. Apparatus as claimed in claim 4. wherein said guide wheel pivotposition is proportioned to the lateral movement of said downstreamvertical guide pair through said pivoted linkage.

References Cited UNITED STATES PATENTS Caskin 154-42 Lehmacher et a1.156-495 Nagano 156-505 Byrt 156-505 Ziebolz 242-76 10 Meagher, Jr., eta1 26-66 6 OTHER REFERENCES Hibbard et 211., Document Feeding andAligning,

IBM Technical Disclosure Bulletin, vol. 4, No. 8, January 1962, p. 1.

WILLIAM A. POWELL, Primary Examiner B. J. LEITTEN, Assistant ExaminerUS. Cl. X.R.

